Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 57, 00014, Finland.
Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 57, 00014, Finland.
Vet J. 2019 Sep;251:105345. doi: 10.1016/j.tvjl.2019.105345. Epub 2019 Jul 27.
A constant rate infusion (CRI) of medetomidine is used to balance equine inhalation anesthesia, but its cardiovascular side effects are a concern. This experimental crossover study aimed to evaluate the effects of vatinoxan (a peripheral α2-adrenoceptor antagonist) on cardiorespiratory and gastrointestinal function in anesthetized healthy horses. Six horses received medetomidine hydrochloride 7μg/kg IV alone (MED) or with vatinoxan hydrochloride 140μg/kg IV (MED+V). Anesthesia was induced with midazolam and ketamine and maintained with isoflurane and medetomidine CRI for 60min. Heart rate, carotid and pulmonary arterial pressures, central venous pressure, cardiac output and arterial and mixed venous blood gases were measured. Selected cardiopulmonary parameters were calculated. Plasma drug concentrations were determined. Fecal output was measured over 24h. For statistical comparisons, repeated measures analysis of covariance and paired t-tests were applied. Heart rate decreased slightly from baseline in the MED group. Arterial blood pressures decreased with both treatments, but significantly more dobutamine was needed to maintain normotension with MED+V (P=0.018). Cardiac index (CI) and oxygen delivery index (DOI) decreased significantly more with MED, with the largest difference observed at 20min: CI was 39±2 and 73±18 (P=0.009) and DOI 7.4±1.2 and 15.3±4.8 (P=0.014)mL/min/kg with MED and MED+V, respectively. Fecal output or plasma concentrations of dexmedetomidine did not differ between the treatments. In conclusion, premedication with vatinoxan induced hypotension, thus its use in anesthetized horses warrants further studies. Even though heart rate and arterial blood pressures remained clinically acceptable with MED, cardiac performance and oxygen delivery were lower than with MED+V.
咪达唑仑和氯胺酮诱导麻醉，异氟醚和咪达唑仑持续输注维持麻醉，6 匹马麻醉后股静脉输注盐酸右美托咪定 7μg/kg（MED 组）或盐酸右美托咪定 7μg/kg 复合盐酸伐替可胺 140μg/kg（MED+V 组）。记录心率、颈动脉和肺动脉压、中心静脉压、心输出量、动脉血气和混合静脉血气，计算相关心功能和肺功能参数。监测 24 小时粪便排出量，测定血浆药物浓度。采用重复测量协方差分析和配对 t 检验进行统计学分析。与基础值相比，MED 组心率轻度下降，两组动脉压均下降，MED+V 组需要更多的多巴酚丁胺维持正常血压（P=0.018）。与 MED 组相比，MED+V 组心输出量指数（CI）和氧输送指数（DOI）下降更明显，20min 时差异最大：CI 分别为 39±2 和 73±18（P=0.009），DOI 分别为 7.4±1.2 和 15.3±4.8（P=0.014）。两种处理粪便排出量或血浆右美托咪定浓度无差异。结论：麻醉前应用伐替可胺可导致低血压，因此其在麻醉马中的应用需要进一步研究。尽管 MED 组的心率和动脉血压仍在临床可接受范围内，但心脏功能和氧输送均低于 MED+V 组。
